From 54f3fb127d9c265a5724d193e5c7c6db29fb4150 Mon Sep 17 00:00:00 2001 From: Haiyue Wang Date: Thu, 25 Jun 2020 11:50:46 +0800 Subject: [PATCH] bus/pci: fix VF memory access To fix CVE-2020-12888, the linux vfio-pci module will invalidate mmaps and block MMIO access on disabled memory, it will send a SIGBUS to the application: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=abafbc551fdd When the application opens the vfio PCI device, the vfio-pci module will enable the bus memory space through PCI read/write access. According to the PCIe specification, the 'Memory Space Enable' is always zero for VF: Table 9-13 Command Register Changes Bit Location | PF and VF Register Differences | PF | VF | From Base | Attributes | Attributes -------------+--------------------------------+------------+----------- | Memory Space Enable - Does not | | | apply to VFs. Must be hardwired| Base | 0b 1 | to 0b for VFs. VF Memory Space | | | is controlled by the VF MSE bit| | | in the VF Control register. | | -------------+--------------------------------+------------+----------- Afterwards the vfio-pci will initialize its own virtual PCI config space data ('vconfig') by reading the VF's physical PCI config space, then the 'Memory Space Enable' bit in vconfig will always be 0b value. This will make the vfio-pci treat the BAR memory space as disabled, and the SIGBUS will be triggered if access these BARs. By investigation, the VF PCI device *passthrough* into the Guest OS by QEMU has the 'Memory Space Enable' with 1b value. That's because every PCI driver will start to enable the memory space, and this action will be hooked by vfio-pci virtual PCI read/write to set the 'Memory Space Enable' in vconfig space to 1b. So VF runs in guest OS has 'Mem+', but VF runs in host OS has 'Mem-'. Align with PCI working mode in Guest/QEMU/Host, in DPDK, enable the PCI bus memory space explicitly to avoid access on disabled memory. Fixes: 33604c31354a ("vfio: refactor PCI BAR mapping") Cc: stable@dpdk.org Signed-off-by: Haiyue Wang Acked-by: Anatoly Burakov Tested-by: Harman Kalra Tested-by: David Marchand Tested-by: Thierry Martin --- drivers/bus/pci/linux/pci_vfio.c | 37 ++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) diff --git a/drivers/bus/pci/linux/pci_vfio.c b/drivers/bus/pci/linux/pci_vfio.c index 64cd84a689..ba60e7ce99 100644 --- a/drivers/bus/pci/linux/pci_vfio.c +++ b/drivers/bus/pci/linux/pci_vfio.c @@ -149,6 +149,38 @@ pci_vfio_get_msix_bar(int fd, struct pci_msix_table *msix_table) return 0; } +/* enable PCI bus memory space */ +static int +pci_vfio_enable_bus_memory(int dev_fd) +{ + uint16_t cmd; + int ret; + + ret = pread64(dev_fd, &cmd, sizeof(cmd), + VFIO_GET_REGION_ADDR(VFIO_PCI_CONFIG_REGION_INDEX) + + PCI_COMMAND); + + if (ret != sizeof(cmd)) { + RTE_LOG(ERR, EAL, "Cannot read command from PCI config space!\n"); + return -1; + } + + if (cmd & PCI_COMMAND_MEMORY) + return 0; + + cmd |= PCI_COMMAND_MEMORY; + ret = pwrite64(dev_fd, &cmd, sizeof(cmd), + VFIO_GET_REGION_ADDR(VFIO_PCI_CONFIG_REGION_INDEX) + + PCI_COMMAND); + + if (ret != sizeof(cmd)) { + RTE_LOG(ERR, EAL, "Cannot write command to PCI config space!\n"); + return -1; + } + + return 0; +} + /* set PCI bus mastering */ static int pci_vfio_set_bus_master(int dev_fd, bool op) @@ -427,6 +459,11 @@ pci_rte_vfio_setup_device(struct rte_pci_device *dev, int vfio_dev_fd) return -1; } + if (pci_vfio_enable_bus_memory(vfio_dev_fd)) { + RTE_LOG(ERR, EAL, "Cannot enable bus memory!\n"); + return -1; + } + /* set bus mastering for the device */ if (pci_vfio_set_bus_master(vfio_dev_fd, true)) { RTE_LOG(ERR, EAL, "Cannot set up bus mastering!\n"); -- 2.20.1